Telephone system.



A. D. T. LIBBY.

TELEPHONE SYSTEM.

APPLIOATION FILED nov. a, 1909.

- lnvenfb'r Albion [7. 77 L119 0 A Patented May 31, 1910.

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UNITED STATEQ BTENT OFFICE.

ALBION ID. 1!. LIBBY,

OI EIIYBIA, OHIO,

0F ELYRIA, OHIO, ASSIG'NOR TO THE DEAN ELECTRIC COMPANY,

A CORPORATION OF OHIO.

TELEPHONE SYSTEM.

959,765. Original application flied Hay 2B, 1909,

Specification of Letters Patent.

Patented May 31, 1910.

Serial, No. 498,911. Divided and this application filed November 8,

1908. Serial No. 526,814.

To all whom it may concern:

Be it known that I, ALBION D. T. LIBBY, a citizen ofthe United States, residing at Elyria, in the count of Lorain and State of Ohio, have invente certain new and useful Im rovements in Telephone Systems; and I 0 hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to make and use the same.

This ap lication is a division of my application, gerial No. 498,911, filed May 28, 1909.

My invention relates to telephone systems, and more particularly to that class of telephone systems in which a plurality of telephone lines lead to a central station where they may be connected together for conversational purposes by means of cord or other arrangements. Central station circuits of: the general character which mine represents, heretofore in use, have been divi ed into two general classes known as three and twoconductor cords. The former consists of two strands, one of which is common to the talking and supervisory signal arrangements, and utilizes a two-conductor plug, thereby realizing the advantages of simplicity and cheapness in manufacture,a greater certainty in operation, and longer life. Against these merits there exists in this former circuit the faults of a common conductor for the calling and signaling currents, both of which necessarily operate over the same strand. The other form of cord circuit, namely, the three-conductor cord, provides a different circuit for these two clases of current, thus liberating the talking circuit from the objectionable burden of transmitting the supervisory currents. On the other hand, the three-conductor plugs, which have been invariably used and inalienably associated with these circuits, reguire more trouble and expense in their prouction, are less efficient, require more care in operating, and are shorter lived than the two-conductor plug. v

By my invention I pro use to produce a central station circuit a a ted to connect the subscribers lines toget er in which I combine the use and advantages of a twoconductor plug with a three-conductor cord, thus being1 enabled to realize the cheapness and simp city of the former and superior service of the latter. I remove the burden of transmitting the supervisory si aling currents from the talking strands, aving, 1n fact, produced a cord circuit in which the signaling is performed over conductors independent o the talking circuit. To do this, I produce a system in which I may connect two cord strands to the sleeve of the plug, making the said sleeve large enough to engage both the sleeve spring and the ring of the jack when the plug is inserted therein. The talking current passes through the sleeve of the jack to the forward part of the plug without passing to the third strand om which it is excluded by the reactance of the supervisory relay and through reacting means which may be provided without departing from the s irit of my invention. On the other hand, t e continuous current which controls the signals being excluded from the talking circuit by the cord condenser, traverses the ring of the jack and the rear of the plug sleeve and passes on to the battery. Thus, it will be seen that I produce a cord circuit using the two-con notor plug in which the talking circuit is independent of and distinct from the circuit of the supervisory apparatus.

In this preliminary description I have ondeavored to explain the main pur ose of my invention, and in so doing have described a articular form of apparatus and a particuar mode of 0 ration. This has been done to elucidate t e purpose, the means and a method of realizing such purpose, and not with the intention of limiting my invention or my objects thereto. On the contrary, I intend to realize any and all the benefits of an modifications and methods which are included within the see c of my claims, as well as the functions 0 such modifications or methods,

My invention will be better understood by reference to the following description when taken in connection with the accompanying illustrations showing specific embodiments thereof, while its sco e will be more particularly pointed out in t e appended claims.

Figure 1 shows a cord circuit constructed in accordance with my invention. Fig. 2 shows a modification of Fig. 1.

At A I show a substation upon a line 1-2 which extends to the jack J at the central station H. At 0, C, G, and O, I show a plurality of stations upon line 3-4-. which 27 ]9-6*-S-20-to the ne ative extends therefrom to a jack J at the some central station H. The line relay of the line 1-2 is shown at R the line lamp at L and the cutoff relay at The corresponding parts of the line 3-4 are shown at R", L and B. Between these stations is shown a cord circuit terminating in the answering plug P and the calling plug 1 The answering tip supervlsory relay 15 shown at T. The answering sleeve supervisory relay at S The answering supervisory slgnal at D. The calling tip supervisory relay at T and the corresponding sleeve relay at S The answering supervisory signal at D.

The cord strands are divided into sections by condensers K and K. The condenser K divides the tip strands into the sections 5 and 7. The condenser K divides the sleeve strand into the sections 6 and 8. At F, F,

F, F I show empirically contacts which lead to the sources of signaling current.

The plug P and the answering end of the cord do not differ from that of the common two-conductor cord. The calling end, however, is shown, according to my invention,

and the third strand 9 leading to the sleeve 10 which is common to said third strand and to the sleeve talking strand 8.

The particular description of my invention can be best described by the operation which is as follows: Assuming that the subscriber at A desires to communicate with the subscriber C on the line 3-i, subscriber A removes his receiver from the book which closes the substation circuit in bridge of the line, permitting the flow of direct current which, revious to this operation, was prevented the condenser K*. A circuit is thus completed through the line relay R as follows: ground at G batter'y B-R --11 1-station A-thc contacts of the switch hook thereat-2-13-14ground at G. The relay R is energized pulling up its armature 15, closing a circuit through the line lamp L--through ground G-battery B-15--16L-G. This vitalizes the lamp L, attracting the attention of the central station operator who inserts the plug P into the line jack J, completing a circuit through the cut-off relay R as follows: ground at G -R-17-ring 18slecve 196-S 20-battery B9.1-ground at Gt. This energizes relay R which ulls up its armatures 19. and 13 cutting oil the line from the ground and the line relay, causing the ex tinction of the lamp L. The supervisory relay S is also energized by current flowing over this circuit, pulling up its armature 22 which would complete the circuit of the su' pervisory lamp D were not a second circuit sunultaneousl completed through the tip relay T. This circuit is as follows: sitive pole of battery B-23-24--T -5-t1p 25- tip spring 26--2-substation circuit A-1 ole of battery 13. The tip relay T eing tlius energized, pulls up its armature 30 interrupting the circuit of the signal I) and preventing its operation. The central station operator now connects her listening set (not shown) into the cord circuit ascertaining the desired connection. Being informed that the substation C is desired, she next tests the line, and, finding it not busy--which assumption is made in this 0peration-she inserts the plu P into the jack J. A circuit is immediate y completed through the relays R and S as follows: from ground at G 2l-battery B-31-S 910-ring 3i2- R' to ound at G". This energizes relay R cutting off the line signaling apparatus of the line 34. The relay 8* is energized pulling up its armatures 33 and 34.. Thearmature 33 completes a circuit through the lamp D as follows: positive pole of battery B23--D'--363738-3533-31negative pole of battery B. This vitalizes the lamp D The armature 34 closes the switch 3H0, placing the battery B in bridge of the calling end of the cord as follows: from 10-9S -31-B-23-4=lT -4O3 i 42 to the tip side 7. The operator new places ringing current on the line, selecting the station 0, who, upon answering, removes his receiver from the hook closing a substa tion bridge thereat. The tip relay T is immediately energized over the bridge just described, the tip side of the cord circuit and the line of the now closed substation circuit. The armature 37 is attracted interrupting the circuit of the signal D. The armature 45 is attracted, closing the switch 45-46 and completing the cord circuit therethrough. The parties now converse through the following circuit: from the substation A-127--196K8-10-47-4C- 3-4=8l9--50-45-4:6-K--5-25-26- -2---back to substation A. It will thus be seen that the talking circuit of the calling end of the cord is independent of and distinct from the circuit of the sleeve supervisory and cut-ofi relay. Upon the termination of the conversation the subscribers return their receivers to the books which action interrupts the previously described circuits of the tip relays T and T which are dencrgized, permitting their arnnltenss to fall back and close the circuits of the supervisory lamps which are operated to indicate the desire for disconnection. The operator then pulls out the plugs, restoring the system to normal.

In Fig. 2 I show a modification conform ing in every particular to the circuit shown in Fig. 1, except that both plugs are constructed in accordance with my invention, the sleeve 19 of the plug P serving both for the talkiu strand and an additional strand which leads to the supervisory relay S independently of the talking strand. The operation is the same as that described, except that the cut-ofi relay R and the relay 3 are operated over the Lllll'd strand instead of over the talking strand 6 described in the operation supra. The talking now takes lace through the cord strand independent y of the supervisory relays.

While I have shown these embodiments of my invention, which are the p1'eferred ar rangernents, it will be obvious to those skilled in the art to which this lnyention appertains, that numerous and extensive departures from the form and details of the circuits here shown may he made without departing from the spirit of this invention, the same being herein shown solely for the purpose of clearly illustrating my preferred arrangements.

I claim:

1. In a telephone system, a plurality of telephone lines leading from substations to a central exchange, a three-strand cord at said central exchange for connecting two of said lines for conversation, switching means by which said central circuit is connected to said lines, two of said strands connected directly to a common contact of said switching means to complete two independent circuits in said cord.

'2. In a telephone system the combination of a plurality of subscribers lines extending from sub-stations to an exchange, a three conductor link at the exchange for connecting said lines together, said lines terminating in spring jacks, a two conductor plug for said link, two of said strands being connected directly to the same contact of said plug, a cut-off relay, a source of current in said link, a circuit for said relay completed when said plug is inserted into a jack of a line, a talking circuit completed when two of said lines are linked together, said talking circuit and said cut-oil relay circuit having but one common point, said source supplying current to said talking circuit through a partof said cut-ofi' relay circuit to said common point.

In a telephone system, the combination of a plurality of telephone lincs,sub-stations on said lines, an exchange to which said lines lead, spring jacks in which said lines terminate, a three conductor link at said exchange for connecting said lines together, a two contact plug connected to said link to be inserted in one of said jacks, a source of current at the exchange, a supervisory relay, a conductor leading from said source a two contact plug connected to said ink to be inserted in one of said jacks, a supervisory signal in said link, means for 'controlling said signal associated with said link, a circuit for said means connected to one of the contacts of said plug, a talking circuit through said plug, the talking circuit being free from the current through the circuit of said supervisory signal controlling means.

5. In a telephone system; the combination of a plurality of telephone lines, sub-stations on said lines, an exchange to which said lines lead, spring jacks, in which said lines terminate, a three conductor link at Said exchange for connecting said lines together, a two contact plug connected to said link to be inserted in one of said jacks, a supervisory relay, a circuit therefor leading through a contact of said plug, a talking circuit throu 11 said contact, said talking circuit being ires from the current through said relay circuit.

6.- In a telephone system the combination of a plurality of telephone lines,sub-stations on said lines, an exchange to which said lines lead, a link at said exchange for connecting said lines together, a source of current, switching means for connecting a line to said link, a pair of talking strands in said link, a third strand leading to said source, a switch contact to which said third strand and one of said talking strands is connected, two line contacts with which said first named contact engages when said link and line are united and a separate circuit through said third conductor, said talking circuit being free from current through said separate circuit.

In testimony whereof I aiiix my signature in presence of two witnesses.

ALBION D. T. LIBBY.

\Vitnesses:

F. O. Rmnnr, C. A. Snvnncoon. 

